4,317 research outputs found
Solar Model Parameters and Direct Measurements of Solar Neutrino Fluxes
We explore a novel possibility of determining the solar model parameters,
which serve as input in the calculations of the solar neutrino fluxes, by
exploiting the data from direct measurements of the fluxes. More specifically,
we use the rather precise value of the neutrino flux, obtained
from the global analysis of the solar neutrino and KamLAND data, to derive
constraints on each of the solar model parameters on which depends. We
also use more precise values of and fluxes as can be obtained from
future prospective data and discuss whether such measurements can help in
reducing the uncertainties of one or more input parameters of the Standard
Solar Model.Comment: 25 pages, 3 figure
Flavor Delta(54) in SU(5) SUSY Model
We design a supersymmetric SU (5) GUT model using \Delta (54), a finite
non-abelian subgroup of SU (3)f . Heavy right handed neutrinos are introduced
which transform as three-dimensional repre-sentation of our chosen family
group. The model successfully reproduces the mass hierarchical mass structures
of the Standard Model, and the CKM mixing matrix. It then provides predictions
for the light neutrino with a normal hierarchy and masses such that m{\nu},1
\approx 5\times10-3 eV, m{\nu}, 2 \approx 1\times 10-2 eV, and m{\nu},3 \approx
5 \times 10-2 eV. We also provide predictions for masses of the heavy
neutrinos, and correc- tions to the tri-bimaximal matrix that fit within
experimental limits, e.g. a reactor angle of -7.31o. A simple modification to
our model is introduced at the end and is shown to also produce predictions
that fall well within those limits.Comment: 22 page
Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology
We analyze the impact of a measurement, or of an improved bound, on
theta_{13} for the determination of the effective neutrino mass in
neutrino-less double beta decay and cosmology. In particular, we discuss how an
improved limit on (or a specific value of) theta_{13} can influence the
determination of the neutrino mass spectrum via neutrino-less double beta
decay. We also discuss the interplay with improved cosmological neutrino mass
searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR
Constraining Mass Spectra with Sterile Neutrinos from Neutrinoless Double Beta Decay, Tritium Beta Decay and Cosmology
We analyze the constraints on neutrino mass spectra with extra sterile
neutrinos as implied by the LSND experiment. The various mass related
observables in neutrinoless double beta decay, tritium beta decay and cosmology
are discussed. Both neutrino oscillation results as well as recent cosmological
neutrino mass bounds are taken into account. We find that some of the allowed
mass patterns are severely restricted by the current constraints, in particular
by the cosmological constraints on the total sum of neutrino masses and by the
non-maximality of the solar neutrino mixing angle. Furthermore, we estimate the
form of the four neutrino mass matrices and also comment on the situation in
scenarios with two additional sterile neutrinos.Comment: 40 pages, 9 figures. Minor changes, matches version in PR
Lepton number violating four-body tau lepton decays
We study the four-body tau^+- -> nu_tau l^+- l^+- X^-+ decays where l=e or mu
and X=pi, K, rho and K^* mesons. These decay processes violate the total lepton
number (|Delta L|=2) and can be induced by the exchange of Majorana neutrinos.
We consider an scenario where these decays are dominated by the exchange of
only one heavy neutrino which produces an enhancement of the decay amplitude
via the resonant mechanism. Searches for these novel decay channels with
branching fractions sensitivities of (10^-7) can provide constraints on the
parameter space of the Majorana neutrinos which are stronger than the ones
obtained from Delta L=2 decays of charged pseudoscalar mesons.Comment: REVTeX, 14 pages, 6 figures, four references added. Version accepted
for publication in PR
Neutrinoless Double Beta Decay and Future Neutrino Oscillation Precision Experiments
We discuss to what extent future precision measurements of neutrino mixing
observables will influence the information we can draw from a measurement of
(or an improved limit on) neutrinoless double beta decay. Whereas the Delta m^2
corresponding to solar and atmospheric neutrino oscillations are expected to be
known with good precision, the parameter theta_{12} will govern large part of
the uncertainty. We focus in particular on the possibility of distinguishing
the neutrino mass hierarchies and on setting a limit on the neutrino mass. We
give the largest allowed values of the neutrino masses which allow to
distinguish the normal from the inverted hierarchy. All aspects are discussed
as a function of the uncertainty stemming from the involved nuclear matrix
elements. The implications of a vanishing, or extremely small, effective mass
are also investigated. By giving a large list of possible neutrino mass
matrices and their predictions for the observables, we finally explore how a
measurement of (or an improved limit on) neutrinoless double beta decay can
help to identify the neutrino mass matrix if more precise values of the
relevant parameters are known.Comment: 35 pages, 12 figures. Comments and references added. To appear in PR
Type II See-Saw Mechanism, Deviations from Bimaximal Neutrino Mixing and Leptogenesis
A possible interplay of both terms in the type II see-saw formula is
illustrated by presenting a novel way to generate deviations from exact
bimaximal neutrino mixing. In type II see-saw mechanism with dominance of the
non-canonical SU(2)_L triplet term, the conventional see-saw term can give a
small contribution to the neutrino mass matrix. If the triplet term corresponds
to the bimaximal mixing scheme in the normal hierarchy, the small contribution
of the conventional see-saw term naturally generates non-maximal solar neutrino
mixing. Atmospheric neutrino mixing is also reduced from maximal, corresponding
to 1 - \sin^2 2 \theta_{23} of order 0.01. Also, small but non-vanishing U_{e3}
of order 0.001 is obtained. It is also possible that the \Delta m^2 responsible
for solar neutrino oscillations is induced by the small conventional see-saw
term. Larger deviations from zero U_{e3} and from maximal atmospheric neutrino
mixing are then expected. This scenario links the small ratio of the solar and
atmospheric \Delta m^2 with the deviation from maximal solar neutrino mixing.
We comment on leptogenesis in this scenario and compare the contributions to
the decay asymmetry of the heavy Majorana neutrinos as induced by themselves
and by the triplet.Comment: 22 pages, 3 figures. Final corrections, matches version in PR
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